Auditory system: development, genetics, function, aging, and diseases

Microtubule and auditory function - an underestimated connection

The organ of Corti, located in the cochlea within the inner ear is the receptor organ for hearing. It converts auditory signals into neuronal action potentials that are transmitted to the brain for further processing. The mature organ of Corti consists of a variety of highly differentiated sensory cells that fulfil unique tasks in the processing of auditory signals. The actin and microtubule cytoskeleton play essential function in hearing, however so far, more attention has been paid to the role of actin. Microtubules play important roles in maintaining cellular structure and intracellular transport in virtually all eukaryotic cells. Their functions are controlled by interactions with a large variety of microtubule-associated proteins (MAPs) and molecular motors. Current advances show that tubulin posttranslational modifications, as well as tubulin isotypes could play key roles in modulating microtubule properties and functions in cells. These mechanisms could have various effects on the stability and functions of microtubules in the highly specialised cells of the cochlea. Here, we review the current understanding of the role of microtubule-regulating mechanisms in the function of the cochlea and their implications for hearing, which highlights the importance of microtubules in the field of hearing research.

Delivery Route and the Outcome of Newborn Hearing Screening of Full-Term Neonates Born in a Public Maternal-Infant Hospital in the South of Brazil

Introduction  The newborn hearing screening (NHS) is the most effective strategy for detecting newborns and infants suspected to have hearing loss. Objective  To verify possible associations between the route of delivery and the results of the NHS conducted at 3 independent times (24, 36, and 36 hours with a facilitator auricular maneuver [FAM]) in the lives of full-term newborns. Methods  A descriptive, observational, prospective study performed with a sample of 462 newborns, with a gestational age ≥ 37 weeks, without risk indicators of hearing loss. The NHS was conducted as a routine element of the facilities, two times: at 24 and 36 hours of life. In the presence of a "failure" in the last test, a new one was immediately performed, following the FAM. Statistic analyses were carried out on the program SPSS version 21.0 (IBM Inc., Armonk, NY, USA). Results  Of the 462 newborns assessed, 304 (65.80%) were born by vaginal delivery. There was a statistical significance of "pass" in the NHS for the 24-hour evaluation ( p  ≤ 0.001 for a vaginal delivery and p  = 0.002 for a cesarean delivery), with the prevalence of the "pass" index being higher when the baby's lifespan was greater. A statistically significant difference was not observed when the NHS results were compared by taking into account the babies' routes of delivery and the different times of life. Conclusion  These findings show that full-term babies who were born by cesarean did not show more "failure" in the NHS results, contradicting the hypothesis of the study. Furthermore, to reduce the false-negative rates, regardless of the route of delivery, this assessment should be conducted after the first 24 hours of the newborns' life.